JPS6317635B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to pressure sensitive copying paper. In particular, a pressure-sensitive microcapsule containing a nearly colorless organic compound (dye) that has color reactivity and a color developer substance (color developer) that can react with the dye to form a colored product. Regarding copy paper. This type of pressure-sensitive copying paper looks almost the same as ordinary paper; the microcapsules are destroyed by writing pressure or typing pressure, and the dye and color developer cause a coloring reaction to produce records. It is generally called carbonless copy paper. Carbonless copying paper has been widely used in recent years as an alternative to carbon copying paper or pigment-type carbon-backed copying paper, and is also called pressure-sensitive copying paper or carbonless carbon paper due to its function. Various forms have been proposed, but in general, microcapsules containing an oil-based liquid in which a dye is dissolved and a color developer are coated on different supports in combination, or they are coated on the front and back sides of the same support. When the microcapsules and the color developer layer are stacked facing each other, and the microcapsules are destroyed by pressure, the oil-based liquid that has dissolved the dye contained therein comes into contact with the color developer layer facing each other. The most commonly used are those that produce color and produce copies. The most important element in pressure-sensitive copying paper is a microcapsule that encloses an oily liquid in which a dye is dissolved, and various microcapsules and methods for producing the same have been proposed. As the most classical method, a production method using coacervation based on liquid-liquid phase separation of a hydrophilic polymer electrolyte colloid is known. For example, there are US Pat. No. 2,800,457 and US Pat. No. 2,800,458. That is, an oily liquid in which a dye is dissolved in an aqueous solution of gelatin, gum arabic, etc. is emulsified and dispersed in fine particles, and a hydrophilic polymer electrolyte colloid is deposited on the surface of the oil droplets to form a coacervate.
It is further cured to obtain microcapsules. Furthermore, in addition to this, there are methods to make microcapsules by causing phase separation of polymer film-forming substances on the surface of minute oil droplets and insolubilizing them, and polymerization of low-molecular monomers or initial polymers using catalysts and curing agents. Alternatively, two types of substances that react with each other to form an insoluble film at the interface of a hydrophilic and hydrophobic liquid are There are known methods of forming microcapsules by dissolving and emulsifying them in a hydrophobic liquid and a hydrophobic liquid to cause an interfacial reaction. The thus obtained microcapsules containing an oily liquid containing a dye dissolved therein are coated on a support together with a suitable binder and dried to obtain pressure-sensitive copying paper. Commonly used binders include polyvinyl alcohol, dextrin, starch, modified starch, carboxymethyl cellulose, casein, and the like. These water-soluble polymer substances become a strong resin by coating and drying, and serve to connect the microcapsules and the support. Furthermore, it has been found that the binder not only has the effect of binding the microcapsules, their buffering agents, fillers, etc. to the support, but also has a great effect as a buffering agent that protects the microcapsules themselves from external pressure. In particular, when using microcapsules with low strength or a film with poor elasticity, the microcapsules are crushed by external pressure that is not intended to produce color, causing so-called stains and sensitivity. This brings about undesirable results in terms of practical use and commercial value as pressure copying paper. However, although many of the above-mentioned water-soluble polymer substances become strong resins after coating and drying, they lack elasticity and are brittle against pressure applied to the microcapsule surface, especially static pressure applied from the vertical direction to the support. , and the buffering effect on the microcapsules was often not fully utilized. Moreover, many of the above-mentioned binders are natural products, and as a result, dispersions for smearing prepared with microcapsule buffers and the like are easily perishable and have the disadvantage that long-term storage is difficult. Furthermore, many of these binders have relatively low soluble concentrations, and the dissolved liquid has a fairly high viscosity, which inevitably causes problems in the smearing process. The present inventor added a water-soluble acrylic acid ester polymer to the microcapsules and a coating layer such as a buffer to protect the microcapsules from external pressure that is not intended to cause color development, and
By linking microcapsules, buffering agents, etc. to a support, we succeeded in obtaining pressure-sensitive copying paper that does not cause natural color development or a decrease in copy density, and also shows no deterioration in quality over time. A further object of the present invention is to reduce the tendency of coating liquids to rot by using a water-soluble acrylic acid ester polymer as an additive in the microcapsule layer.
Another object of the present invention is to make it possible to produce a coating liquid with high concentration and low viscosity. This is because the water-soluble acrylic acid ester polymer can be dissolved in water at high concentration and low viscosity. This effect is achieved in the coating process, especially when applied to high-concentration smearing methods.
These are truly favorable conditions. Among the water-soluble acrylic ester polymers used in the present invention, representative examples of polyacrylic ester include polyacrylic acid methyl ester, polyacrylic acid ethyl ester, polyacrylic acid propyl ester, polyacrylic acid butyl ester, etc. Polyacrylic acid butyl ester is particularly preferred. Water-soluble polyacrylic esters may contain some isopropyl alcohol, ethyl alcohol, etc. due to the polymer manufacturing process, but these do not have any adverse effects on microcapsules. Additionally, water-soluble acrylic ester-methacrylic ester copolymers are also commercially available, but they exhibit similar effects to polyacrylic esters. In addition, the polymer of water-soluble acrylic acid ester as used in the present invention refers to a polymer containing an acrylic acid ester as a monomer unit, and also includes copolymers with other monomers. A feature of the present invention is that the purpose can be achieved simply by adding a water-soluble acrylic acid ester polymer to the coating liquid. That is, the purpose can be easily achieved without complicating the process. Another feature is that it can serve its purpose without any loss in performance of pressure sensitive copying paper. Generally, in order to solve friction and stains, it is necessary to add a large amount of particles and/or pigments that can act as buffering agents, which results in a decrease in copy density and impedes the original mission of pressure-sensitive copying paper. There are many cases of loss. However, the water-soluble acrylic acid ester polymer of the present invention can completely achieve the purpose without any loss in quality as a pressure-sensitive copying paper. The amount of the water-soluble acrylic acid ester polymer used in the present invention is based on the solid weight of the microcapsules.
5 to 50 parts per 100 parts, more preferably 20 to 40 parts
It is desirable to add within the range of 100%. Any color former and color developer can be used in the pressure-sensitive copying paper of the present invention. As the coloring agent, for example, crystal violet lactone, benzoylleucomethylene blue, Michler's hydrol, fluorans, spiropyrans, etc. can be used, and as the coloring agent, acid clay, salicylate, phenolic resin, etc. can be used. Next, specific methods will be shown in Examples. (In the examples, "parts" indicate parts by weight.) Reference Example 1 200 parts of Hysol SAS N-296 (manufactured by Nisseki Chemical Co., Ltd., high-boiling hydrocarbon oil) was added with CVL (crystal violet lactone). Colorless dye for pressure copying paper) 6.0
The mixture was heated and dissolved to form an oily liquid. After emulsifying the above oily liquid in 200 parts of a 5.0% aqueous solution (PH5.8) of styrene maleic anhydride copolymer, 20 parts of melamine, 45 parts of 37% formalin solution, water
35 parts were heated and dissolved at pH 9.5 to obtain a melamine-formalin initial condensate, which was added to the above emulsion and stirred.
The reaction was carried out at 75°C for 1.5 hours. Cool to room temperature and adjust the pH
It was set at 9.5. The microcapsule dispersion obtained above was used as microcapsules for Examples. Example 1 Using the microcapsule dispersion obtained in Reference Example 1, a microcapsule coating liquid was adjusted to have a total solids concentration of 18% using the following formulation. Microcapsules 100 parts (solid) Wheat starch 25 parts Butyl polyacrylate (polyacrylate SR-131, manufactured by Goo Kagaku Co., Ltd.) 30 parts (fixed) The obtained coating liquid was coated on 41 g/ ^m2 high-quality paper. 4.5~5.0
Apply with a Mayer bar so that it is g/ ^m2 ,
It was dried to obtain pressure-sensitive copying paper. Above, upper paper and commercially available lower paper (Mitsubishi NCR paper phenol resin coated N
-40), overlapping them so that the coated surfaces are facing each other,
Cut by guillotine. At this time, the lower paper sheet turned blue only slightly, and when the reflectance of the blued portion was measured using a color difference meter, it was 94.0%. Example 2 In place of the polybutyl acrylate used in Example 1, a butyl acrylate ester-methacrylate ester copolymer (Plasize L-53P, manufactured by Gooh Kagaku) was used, and the same formulation as in Example 1 was made. The solution was prepared using Apply the obtained coating liquid to 41g/ ^m2 high-quality paper with 4.5~5.0
g/m ² using a Mayer bar to obtain pressure-sensitive copying paper. It was cut using a guillotine in the same manner as in Example 1. At this time, the bottom paper sheet turned only slightly blue, and using a color difference meter,
When we measured the reflectance of the blued area, it was 94.0%.
It was hot. Comparative Example 1 Example 1 and Example 2 in which the same weight part of starch adhesive (Nippon Shokuhin Co., Ltd. MS-3800) was added instead of the acrylic ester polymer in the formulation in Example 1. Table 1 shows the results of the same pressure test as above, as well as color development, storage stability, and viscosity. Comparative Example 2 Example 1 and Example 2 when the same weight part of polyvinyl alcohol (Nippon Gosei Kagaku Co., Ltd. NM-11) was added instead of the acrylic ester polymer in the formulation in Example 1. Table 1 shows the results of similar guillotine cutting, color development, storage stability, and viscosity. The color development is based on the color development of the bottom paper after 1 minute when a sheet of commercially available bottom paper (Mitsubishi NCR paper coated with phenol resin, N-40) is passed between rolls under a pressure of 15 kg/cm to develop color. Shows the value read by a color difference meter. (The smaller the value, the better the color development is.Reflectance%). Preservability indicates the state of decay when the obtained liquid is exposed to the outside air for two weeks.

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Claims (1)

[Claims] 1. A microcapsule layer containing an oil-based liquid in which a dye is dissolved and a color developer layer are provided on different supports, or on the front and back sides of the same support. A pressure-sensitive copying paper characterized by containing a water-soluble acrylic acid ester polymer in a microcapsule layer containing a dissolved oily liquid.